Tekin HT rotors any different?

[jrowles91]

I got a Tekin 13.5 Redline motor in a trade that's going in my Wraith. The guy I got it from ground the output shaft (by mistake supposedly) and now the pinion wobbles ever so slightly. I emailed Tekin support and they said for the application their 13mm HT rotor is a great replacement. As of now I'm running it fine but if it starts chewing up bearings or my spur I'll likely change it out. Does anyone have any experience with this? Is there really much difference? Thanks!!

TowerHobbies.com | Tekin 13.0mm Redline S BL Torque Rotor

[EddieO]

Bigger Rotors mean more torque and efficiency, but less RPM and often overall power. So you might notice a drop in overall HP....might need to use adjust your gearing to use the power correctly.

Later EddieO

[jrowles91]

OK that makes sense. I don't cafe so much about the speed. I think 3500kv is to high anyway so losing a bit of top end will be OK. On same gearing, will there be a noticeable difference?

[AddictedtoRC1]

I replaced the stock rotor in my 13.5 with the HT 13mm and it makes quite an improvement in torque and smoothness. Start up is smoother and wheelspeed isn't affected enough to really notice. If you are gonna replace yours I would recommend the HT for sure.

[jrowles91]

Awesome to hear!!! That's exactly what I wanted to hear lol. Question though, why not go for the 13.5 or 14 km HT rotor? Wouldn't that give even more torque?

[AddictedtoRC1]

Yes it would. I went with 13 to try and keep a balance between torque/smoothness and top end. The Redline already has plenty of power as is anyway. It's just what I went with I guess.

[jrowles91]

That's a good point. Seems like no one has the 14mm for sale anyway. Thanks for the input! Was very helpful.

[Olle P]

Originally Posted by EddieO

Bigger Rotors mean more torque and efficiency, but less RPM and often overall power. ...

Really?
Looking at the data sheet for different Novak Ballistic motors it seems that power and efficiency stays the same, only Kv rating differs.

[EddieO]

Yes really. When you decrease the air gap, the torque will go up and rpm down. Often this change results in more rpm loss than torque gained, so overall power goes down. The larger rotors are always more efficient and they typically run cooler too.

It's very rare to find something in our motors that is not a trade off, just how they work.

Dyno any brushless and change rotors and you will see the same thing.....it's hardly a perfect science though.

Later EddieO

Originally Posted by Olle P

Really?
Looking at the data sheet for different Novak Ballistic motors it seems that power and efficiency stays the same, only Kv rating differs.

[Olle P]

Thinking of it I think it depends a bit on the definition of "power":
Let's assume the momentary peak power from a cool motor goes down, as you say.
Assuming also that the part of increased efficiency is correct.
Then in use the motor won't heat up that fast, so since (for example) Novak's power ratings are the given maximum (average) power it can deliver during a six minute run without overheating the increased efficiency will balance out the loss in peak power.

[EddieO]

There is one definition of power, rpmxtorque. In RC motors its not used any other way I have ever seen.

And there is no dyno I know of that constantly runs a motor for 6 minutes to avg out the power. I've seen the Novak dyno and know that while its their own design, it works like any other dyno.

Certainly not the industry standard way of rating motors. While some races are 6 minutes, others are 8.....some are even more. What if the person is not even racing? You want your motor to look less powerful than the other companies?

I've dynoed the Novak motors using the tuning rotors. In all cases the bigger rotors made less power because of a bigger drop in RPM than Torque gained........and they were all more efficient. This isn't exclusive to Novak, all the other motor companies motors will give similar results. Some times the gain/loss is closer, sometimes bigger....the efficiency gain can vary also.

It's certainly not a bad thing, just how are little motors work.

Later EddieO

Originally Posted by Olle P

Thinking of it I think it depends a bit on the definition of "power":
Let's assume the momentary peak power from a cool motor goes down, as you say.
Assuming also that the part of increased efficiency is correct.
Then in use the motor won't heat up that fast, so since (for example) Novak's power ratings are the given maximum (average) power it can deliver during a six minute run without overheating the increased efficiency will balance out the loss in peak power.

[Olle P]

Originally Posted by EddieO

There is one definition of power, rpmxtorque. In RC motors its not used any other way I have ever seen.

We've already had that discussion.

You're correct that motor speed times the torque is the way "power" is defined. But it's not what's used when manufacturers present the "power" of their motors.

[EddieO]

No, companies don't really mix the two either.

As discussed in the previous thread, companies went from using the watts rating for motors to using just KV to show how fast the motor was. Why, I dunno.......

A quick look on two sites, Novak and Castle, both clearly define KV and watts as two different ratings. While some motors just have a KV rating, it clearly not being defined as power, but as KV or RPM per Volt.

Why we are off on this strange discussion is beyond me.....the simple fact, the bigger rotors will provide more torque at the cost of RPM, the gain is often less than the loss, which results in a less powerful motor that typically will be more efficient. Design elements can reduce the gains and losses.



Later EddieO

Originally Posted by Olle P

We've already had that discussion.

You're correct that motor speed times the torque is the way "power" is defined. But it's not what's used when manufacturers present the "power" of their motors.

[JohnRobHolmes]

The larger rotors don't start up as well, but they do produce torque with better efficiency. More accurately, for a given amp draw they will produce more torque and for a given KV the motor has less terminal resistance. This will increase the loaded efficiency a touch. I typically only recommend them to people that are having problems with heat, stalling, or brake strength. A person that does mostly low speed/ low load crawling has no need for the larger rotor, and may even see a run time decrease because of the higher no load amperage and power wasted during motor startup.

If the rotor is getting replaced anyway, the 13mm is a better choice than the 14mm. Startup is very abrupt with the 14mm. I personally don't like the 13mm either, my preference of low speed control likes the stock rotor better. The airgap may be a mile wide, but it does the job with proper gearing and voltage.

[jrowles91]

Originally Posted by JohnRobHolmes

The larger rotors don't start up as well, but they do produce torque with better efficiency. More accurately, for a given amp draw they will produce more torque and for a given KV the motor has less terminal resistance. This will increase the loaded efficiency a touch. I typically only recommend them to people that are having problems with heat, stalling, or brake strength. A person that does mostly low speed/ low load crawling has no need for the larger rotor, and may even see a run time decrease because of the higher no load amperage and power wasted during motor startup.

If the rotor is getting replaced anyway, the 13mm is a better choice than the 14mm. Startup is very abrupt with the 14mm. I personally don't like the 13mm either, my preference of low speed control likes the stock rotor better. The airgap may be a mile wide, but it does the job with proper gearing and voltage.

What would the difference be between the regular 12.5 and the 12.5HT rotor? Is it just the amount of magnetic material?

[JohnRobHolmes]

Tekin doesn't say on the site directly, I would assume it is a higher grade of magnet or a different internal shaft size that changes the steel to magnet ratio. At any rate, a stronger magnetic field.